The invention relates to an arrangement for open-end rotor spinning having a spinning rotor which has a fiber sliding surface expanding conically to form a fiber feeding groove. The mouth of a fiber feeding duct is disposed opposite the fiber sliding surface. The fiber feeding duct starts at an opening roller and tapers in the direction toward the fiber sliding surface. An insert projects into the spinning rotor which is a component of a cover closing a rotor housing which is connected to a vacuum source which takes in an air current through the fiber feeding duct. The fiber feeding duct is provided with at least one bypass opening at a distance from the mouth.
In order to ensure optimum spinning conditions, the fibers transported in the fiber feeding duct by means of the air current should arrive on the fiber sliding wall, on the one hand, at a sufficient distance from the open end of the spinning rotor and, on the other hand, at a sufficient distance from the fiber collecting groove.
By means of the distance to the open end of the spinning rotor, it is to be avoided that the air flowing off by way of the open rotor edge takes along fibers. The distance from the fiber collecting groove is to have the effect that the fibers are stretched and aligned on the fiber sliding surface between the point of arrival and the fiber collecting groove. In modern open-end rotor spinning, a trend exists leading toward progressively smaller spinning rotors so that the operating speeds are higher. In this case, it becomes more difficult to meet the above-mentioned requirements. It is therefore necessary to guide the fibers in a very targeted manner to a certain point of the fiber sliding surface of the spinning rotor. This may be implemented by means of a fiber feeding duct with a small mouth. However, the small mouth has the result that the amount of air of the taken-in air current is reduced so that disturbances may occur in the fiber transport and/or fly in the area of the opening roller.
In order to solve the described problem, it is known from German patent document DE-37 04 460 A1 to enlarge the mouth of the fiber feeding duct in the circumferential direction of the spinning rotor but to keep it as small as possible in the axial direction of the spinning rotor.
It has also become known from German patent document DE-37 30 706 A1 to open up the fiber feeding duct starting from its end located opposite the fiber sliding surface of the spinning rotor by means of a lateral slot so that the cross-section which is decisive for the taken-in amount of air is placed back into an area of the fiber feeding duct having a larger diameter.
It is also known from German patent document DE-31 20 877 A1, corresponding to U.S. Pat. No. 4,459,800, to separate the fibers even before the entry into the spinning rotor from the transport air flow and thus also from fine dirt particles, particularly from dust. For this purpose, the fiber feeding duct is interrupted in the area before it reaches the spinning rotor or is provided with openings having a relatively large cross-section.
It is also known from German patent document DE-19 14 115 A1 to provide a fiber feeding duct of an open-end rotor spinning arrangement with a deflection in the form of a bend. In this construction, dirt contained in the fibers is to be eliminated. For this reason, the fiber feeding duct, in the area of the bending point, is open as a linear extension. Another air intake opening is provided against the transport direction as a linear extension of the second section so that air is taken in here which deflects the fibers in the direction of the second part of the fiber feeding duct in the area of the bending point.
An object of the invention is to develop an arrangement of the initially mentioned type such that, when a mouth of the fiber feeding duct is provided which has a small cross-section, a sufficient current of transport air is taken in.
This object is achieved according to preferred embodiments of the invention in that the at least one bypass opening is provided at a point of the fiber feeding duct which has a larger cross-section than the mouth of the fiber feeding duct, in that the fiber feeding duct is provided with at least one deflection for the fiber transport direction and in that the bypass opening is disposed behind the deflection in the transport direction and in an area facing away from the deflection.
By means of the bypass opening, the intake cross-section may be enlarged so that, despite a small cross-section of the mouth, a sufficiently large amount of air can be taken in. In order not to be subjected to any significant limitations concerning the dimensioning of the bypass opening, it is provided by means of the deflection that the fibers are guided past the bypass opening at a relatively large distance so that the danger of a sucking-off of fibers is relatively small.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.